1. Field
Embodiments described generally relate to the gasification of a hydrocarbon feedstock.
2. Description of the Related Art
Gasification is a high-temperature process usually conducted at elevated pressure to convert carbon-containing materials into carbon monoxide and hydrogen gas. Since this gas is often used for the synthesis of chemicals or synthetic hydrocarbon fuels, the gas is often referred to as “synthesis gas” or “syngas.” Typical feedstocks to gasification processes include petroleum-based materials that are neat or residues of processing materials, such as heavy crude oil, coals, bitumen recovered from tar sands, kerogen from oil shale, coke, and other high-sulfur and/or high metal-containing residues; gases; and various carbonaceous waste materials. The feedstock materials can be reacted, e.g., in a gasifier, in a reducing (oxygen-starved) atmosphere at high temperature and (usually) high pressure. The resulting syngas typically contains about 85 percent of the feedstock's carbon content as carbon monoxide, with the balance being a mixture of carbon dioxide and methane.
A general approach to gasifying a hydrocarbon feedstock is to select a gasifying temperature that can achieve a very high, e.g., about 96 wt % to about 99 wt %, conversion of the carbon content of the hydrocarbon feedstock. Such approach limits the gasification process to generally highly reactive hydrocarbon feedstocks, e.g., lignite coals. The high temperatures required can also increase the specific consumption of oxidant in the gasification process with the associated high specific consumption of hydrocarbon feedstock per unit of useful syngas (hydrogen and carbon monoxide) produced. Also, in some cases, a gasification temperature that is high enough to achieve a very high carbon content conversion, e.g., about 96 wt % to about 99 wt %, is not practical as such a high temperature can exceed the softening temperature of the particulates e.g., ash, circulating throughout the gasification process. Exceeding the softening temperature of the particulates can result in particulate agglomeration that can prevent the circulation of the particulates and can lead to a stoppage of the gasification process.
There is a need, therefore, for improved systems and methods for gasifying a hydrocarbon feedstock.